1. Field of the Invention
The present invention relates to a supporting device for wiring and piping installed in a space between a base and a rotary base rotatably mounted on the base of an industrial robot.
2. Description of the Related Art
Many conventional supporting devices for wiring of electric cables for industrial robots are installed in interior spaces of the robots for the reasons to keep both a good appearance and free spaces around the industrial robot, and to protect the electric cables. For example, Japanese examined utility model publication No.05006077 and Japanese unexamined patent publication No.02100892 discloses a conventional supporting device for wiring of electric cables for the industrial robot shown in FIGS. 7 and 8. The FIG. 8 is a cross sectional view along the line D--D of FIG. 7.
In FIGS. 7 and 8, the supporting device for wiring of electric cables includes a base 1 having a first space 20 and a rotary base 2 having a second space 21 and rotatably mounted on the base 1. The supporting device includes a pair of elastically flexible conduits 51, 52 each housing a bundle 42 of a plurality of electric cables 42a. The conduits 51,52 are so installed in each of the circular spaces 20,21 between the base 1 and the rotary base 2 on both half sides of each circular space so that they extend in a symmetrically way with respect to a crossing line 25 passing on the rotation axis 0 of the rotary base 2.
Each one end of the conduit 51,52 is secured on the interior wall of the base 1 by a clamp 9 and each conduit 51,52 extends along a halfway in the circular space 20 of the base 1, and then turned back to form an U-shaped configuration 44 and returns along the halfway in the circular space 21 of the rotary base 2 contactably on a ceiling wall of the rotary base 2, and the other end of each conduit 51,52 is secured on the rotary base 2 by a clamp 10. In FIG. 7, a reduction gear 4 is secured to the base 1 and coupled to a driving shaft 24 of a motor 3 secured to the rotary base 2.
By such an arrangement, when the rotary base 2 rotates to one direction, the bundle 42 of a plurality of electric cables 42a housed in one of the conduit 51,52 is made to go forward while bended or turned up with an adequate curvature, further, at the same time, the bundle 42 housed in the other conduit is made to go backward while similarly bended or turned up. This results that the two conduit 51,52 do not interfere with each other, and the bundles 42 housed in the conduits are pressed with a stable load and prevents from wiring troubles.
Another Japanese unexamined publication No.09150393 disclose an arrangement of cables so that each cable draw port is arranged along the rotating direction of a rotary base to prevent cables to fold with each other in a vertical direction.
Year by year, numbers of electric cables and pipes for air or water or the like to be installed in industrial robots are continuously increasing. For example, in an arc spot welding robot performing a predetermined welding work using an end effector such as welding guns gripped by its wrist, a servo motor is recently used to drive an electrode tips in place of an air cylinder. This results that power lines and control lines and pipes for air or water or the like for the servo motors must be added. Further, cables and pipes both for torque-load sensors of torque-load control as well as for vision sensors used in handling robots also increase the numbers of the electric cables and pipes.
However, in the above conventional supporting device for wiring of electric cables shown in FIGS. 7 and 8, when the numbers of the electric cables and pipes increases, the external diameter of the elastically flexible conduit housing electric cables and pipes also increases, resulting that the radius of curvature of the U-shaped configuration 44 increases, and the base and the rotary base must have high vertical heights and large-sized bodies. This also applies to the device of the Japanese unexamined publication No.09150393, because the base and rotary base must have high vertical heights and large-sized bodies to prevent cables and pipes to fold with each other in a vertical direction. These conventional devices inevitably resulted that the robot bodies must have high vertical heights and large-sized.